_____ is Dickens’ first novel of social history reflecting the sharp social contradictions. A: Sketches by Boz B: American Notes C: Martin Chuzzlewit D: Barnaby Rudge

During the first period, Charles Dickens’ major works are: Oliver Twist, and so on. A: American Notes B: A Christmas Carol C: Sketches by Boz D: Dombey and Son

管道系统图一般采用正面斜等测投影绘制，亦即（）。 A: AOX轴处于水平位置 B: BOZ轴铅垂 C: COY轴一般与水平线成45°夹角 D: D三轴的变形系数都是1。